SQL & PL/SQL

Hi,

I m getting error while using foreign key, could you let me know if there is any syntax error.

CREATE TABLE grade(course_no  VARCHAR2(33) NOT NULL,

                                 student_id VARCHAR2(33) NOT NULL,

                                 grade VARCHAR2(2),

                                 CONSTRAINT FK_COURSE

                                 FOREIGN KEY (course_no)  REFERENCES course(course_no)   ON DELETE RESTRICT

                                );

Error report:

SQL Error: ORA-00905: missing keyword

Thanks